But when I try to assign the grid property in the GridGeometry class I get the following error:
qrc:/Scene.qml:40:19: Unable to assign bool to [unknown property type] qrc:/Scene.qml: 40

I'm new in QML so I don't know what I'm doing wrong. I have read the documentation but I' not capable os solving this issue. Any ideas?

The main purpose if to generate a Qt3D scene and assign the data through QML (Grid is a class which contains values at the points that will be rendered using the GridGeometry, derived from Qt3DRender::QGeometry)